Question

[nguyen cam tu]

1/2 + 1/6 + 1/12 + 1/20 1/30

Answer 1

[soyeon_Tiểu bàng giải]

1/2 + 1/6 + 1/12 + 1/20 + 1/30

= 1/1×2 + 1/2×3 + 1/3×4 + 1/4×5 + 1/5×6

= 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6

= 1 - 1/6

= 5/6